package com.sohu.tv.jedis.stat.utils;

import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;

/**
 * A map containing {@code long} values that can be atomically updated. While writes to a
 * traditional {@code Map} rely on {@code put(K, V)}, the typical mechanism for writing to this map
 * is {@code addAndGet(K, long)}, which adds a {@code long} to the value currently associated with
 * {@code K}. If a key has not yet been associated with a value, its implicit value is zero.
 * <p/>
 * <p>Most methods in this class treat absent values and zero values identically, as individually
 * documented. Exceptions to this are {@link #containsKey}, {@link #size}, {@link #isEmpty},
 *  and {@link #toString}.
 * <p/>
 * <p>Instances of this class may be used by multiple threads concurrently. All operations are
 * atomic unless otherwise noted.
 * <p/>
 * <p/>
 * <b>Warning:</b> Unlike {@code Multiset}, entries whose values are zero are not automatically
 * removed from the map. Instead they must be removed manually with {@link #removeAllZeros}.
 *
 * @author Charles Fry
 * @since 11.0
 */
public class AtomicLongMap<K> {
    private final ConcurrentHashMap<K, AtomicLong> map;

    private AtomicLongMap(ConcurrentHashMap<K, AtomicLong> map) {
        this.map = map;
    }

    /**
     * Creates an {@code AtomicLongMap}.
     */
    public static <K> AtomicLongMap<K> create() {
        return new AtomicLongMap<K>(new ConcurrentHashMap<K, AtomicLong>());
    }

    /**
     * Creates an {@code AtomicLongMap} with the same mappings as the specified {@code Map}.
     */
    public static <K> AtomicLongMap<K> create(Map<? extends K, ? extends Long> m) {
        AtomicLongMap<K> result = create();
        result.putAll(m);
        return result;
    }

    /**
     * Returns the value associated with {@code key}, or zero if there is no value associated with
     * {@code key}.
     */
    public long get(K key) {
        AtomicLong atomic = map.get(key);
        return atomic == null ? 0L : atomic.get();
    }

    /**
     * Increments by one the value currently associated with {@code key}, and returns the new value.
     */
    public long incrementAndGet(K key) {
        return addAndGet(key, 1);
    }

    /**
     * Decrements by one the value currently associated with {@code key}, and returns the new value.
     */
    public long decrementAndGet(K key) {
        return addAndGet(key, -1);
    }

    /**
     * Adds {@code delta} to the value currently associated with {@code key}, and returns the new
     * value.
     */
    public long addAndGet(K key, long delta) {
        outer:
        for (; ; ) {
            AtomicLong atomic = map.get(key);
            if (atomic == null) {
                atomic = map.putIfAbsent(key, new AtomicLong(delta));
                if (atomic == null) {
                    return delta;
                }
                // atomic is now non-null; fall through
            }

            for (; ; ) {
                long oldValue = atomic.get();
                if (oldValue == 0L) {
                    // don't compareAndSet a zero
                    if (map.replace(key, atomic, new AtomicLong(delta))) {
                        return delta;
                    }
                    // atomic replaced
                    continue outer;
                }

                long newValue = oldValue + delta;
                if (atomic.compareAndSet(oldValue, newValue)) {
                    return newValue;
                }
                // value changed
            }
        }
    }

    /**
     * Increments by one the value currently associated with {@code key}, and returns the old value.
     */
    public long getAndIncrement(K key) {
        return getAndAdd(key, 1);
    }

    /**
     * Decrements by one the value currently associated with {@code key}, and returns the old value.
     */
    public long getAndDecrement(K key) {
        return getAndAdd(key, -1);
    }

    /**
     * Adds {@code delta} to the value currently associated with {@code key}, and returns the old
     * value.
     */
    public long getAndAdd(K key, long delta) {
        outer:
        for (; ; ) {
            AtomicLong atomic = map.get(key);
            if (atomic == null) {
                atomic = map.putIfAbsent(key, new AtomicLong(delta));
                if (atomic == null) {
                    return 0L;
                }
                // atomic is now non-null; fall through
            }

            for (; ; ) {
                long oldValue = atomic.get();
                if (oldValue == 0L) {
                    // don't compareAndSet a zero
                    if (map.replace(key, atomic, new AtomicLong(delta))) {
                        return 0L;
                    }
                    // atomic replaced
                    continue outer;
                }

                long newValue = oldValue + delta;
                if (atomic.compareAndSet(oldValue, newValue)) {
                    return oldValue;
                }
                // value changed
            }
        }
    }

    /**
     * Associates {@code newValue} with {@code key} in this map, and returns the value previously
     * associated with {@code key}, or zero if there was no such value.
     */
    public long put(K key, long newValue) {
        outer:
        for (; ; ) {
            AtomicLong atomic = map.get(key);
            if (atomic == null) {
                atomic = map.putIfAbsent(key, new AtomicLong(newValue));
                if (atomic == null) {
                    return 0L;
                }
                // atomic is now non-null; fall through
            }

            for (; ; ) {
                long oldValue = atomic.get();
                if (oldValue == 0L) {
                    // don't compareAndSet a zero
                    if (map.replace(key, atomic, new AtomicLong(newValue))) {
                        return 0L;
                    }
                    // atomic replaced
                    continue outer;
                }

                if (atomic.compareAndSet(oldValue, newValue)) {
                    return oldValue;
                }
                // value changed
            }
        }
    }

    /**
     * Copies all of the mappings from the specified map to this map. The effect of this call is
     * equivalent to that of calling {@code put(k, v)} on this map once for each mapping from key
     * {@code k} to value {@code v} in the specified map. The behavior of this operation is undefined
     * if the specified map is modified while the operation is in progress.
     */
    public void putAll(Map<? extends K, ? extends Long> m) {
        for (Map.Entry<? extends K, ? extends Long> entry : m.entrySet()) {
            put(entry.getKey(), entry.getValue());
        }
    }

    /**
     * Removes and returns the value associated with {@code key}. If {@code key} is not
     * in the map, this method has no effect and returns zero.
     */
    public long remove(K key) {
        AtomicLong atomic = map.get(key);
        if (atomic == null) {
            return 0L;
        }

        for (; ; ) {
            long oldValue = atomic.get();
            if (oldValue == 0L || atomic.compareAndSet(oldValue, 0L)) {
                // only remove after setting to zero, to avoid concurrent updates
                map.remove(key, atomic);
                // succeed even if the remove fails, since the value was already adjusted
                return oldValue;
            }
        }
    }

    /**
     * Removes all mappings from this map whose values are zero.
     * <p/>
     * <p>This method is not atomic: the map may be visible in intermediate states, where some
     * of the zero values have been removed and others have not.
     */
    public void removeAllZeros() {
        for (K key : map.keySet()) {
            AtomicLong atomic = map.get(key);
            if (atomic != null && atomic.get() == 0L) {
                map.remove(key, atomic);
            }
        }
    }

    /**
     * Returns the sum of all values in this map.
     * <p/>
     * <p>This method is not atomic: the sum may or may not include other concurrent operations.
     */
    public long sum() {
        long sum = 0L;
        for (AtomicLong value : map.values()) {
            sum = sum + value.get();
        }
        return sum;
    }

    /**
     * Returns true if this map contains a mapping for the specified key.
     */
    public boolean containsKey(Object key) {
        return map.containsKey(key);
    }

    /**
     * Returns the number of key-value mappings in this map. If the map contains more than
     * {@code Integer.MAX_VALUE} elements, returns {@code Integer.MAX_VALUE}.
     */
    public int size() {
        return map.size();
    }

    /**
     * Returns {@code true} if this map contains no key-value mappings.
     */
    public boolean isEmpty() {
        return map.isEmpty();
    }

    /**
     * Removes all of the mappings from this map. The map will be empty after this call returns.
     * <p/>
     * <p>This method is not atomic: the map may not be empty after returning if there were concurrent
     * writes.
     */
    public void clear() {
        map.clear();
    }

    @Override
    public String toString() {
        return map.toString();
    }

  /*
   * ConcurrentMap operations which we may eventually add.
   *
   * The problem with these is that remove(K, long) has to be done in two phases by definition ---
   * first decrementing to zero, and then removing. putIfAbsent or replace could observe the
   * intermediate zero-state. Ways we could deal with this are:
   *
   * - Don't define any of the ConcurrentMap operations. This is the current state of affairs.
   *
   * - Define putIfAbsent and replace as treating zero and absent identically (as currently
   *   implemented below). This is a bit surprising with putIfAbsent, which really becomes
   *   putIfZero.
   *
   * - Allow putIfAbsent and replace to distinguish between zero and absent, but don't implement
   *   remove(K, long). Without any two-phase operations it becomes feasible for all remaining
   *   operations to distinguish between zero and absent. If we do this, then perhaps we should add
   *   replace(key, long).
   *
   * - Introduce a special-value private static final AtomicLong that would have the meaning of
   *   removal-in-progress, and rework all operations to properly distinguish between zero and
   *   absent.
   */

    /**
     * If {@code key} is not already associated with a value or if {@code key} is associated with
     * zero, associate it with {@code newValue}. Returns the previous value associated with
     * {@code key}, or zero if there was no mapping for {@code key}.
     */
    long putIfAbsent(K key, long newValue) {
        for (; ; ) {
            AtomicLong atomic = map.get(key);
            if (atomic == null) {
                atomic = map.putIfAbsent(key, new AtomicLong(newValue));
                if (atomic == null) {
                    return 0L;
                }
                // atomic is now non-null; fall through
            }

            long oldValue = atomic.get();
            if (oldValue == 0L) {
                // don't compareAndSet a zero
                if (map.replace(key, atomic, new AtomicLong(newValue))) {
                    return 0L;
                }
                // atomic replaced
                continue;
            }

            return oldValue;
        }
    }

    /**
     * If {@code (key, expectedOldValue)} is currently in the map, this method replaces
     * {@code expectedOldValue} with {@code newValue} and returns true; otherwise, this method
     * returns false.
     * <p/>
     * <p>If {@code expectedOldValue} is zero, this method will succeed if {@code (key, zero)}
     * is currently in the map, or if {@code key} is not in the map at all.
     */
    boolean replace(K key, long expectedOldValue, long newValue) {
        if (expectedOldValue == 0L) {
            return putIfAbsent(key, newValue) == 0L;
        } else {
            AtomicLong atomic = map.get(key);
            return (atomic == null) ? false : atomic.compareAndSet(expectedOldValue, newValue);
        }
    }

    /**
     * If {@code (key, value)} is currently in the map, this method removes it and returns
     * true; otherwise, this method returns false.
     */
    boolean remove(K key, long value) {
        AtomicLong atomic = map.get(key);
        if (atomic == null) {
            return false;
        }

        long oldValue = atomic.get();
        if (oldValue != value) {
            return false;
        }

        if (oldValue == 0L || atomic.compareAndSet(oldValue, 0L)) {
            // only remove after setting to zero, to avoid concurrent updates
            map.remove(key, atomic);
            // succeed even if the remove fails, since the value was already adjusted
            return true;
        }

        // value changed
        return false;
    }
    
//    private transient Map<K, Long> asMap;

    /**
     * Returns a live, read-only view of the map backing this {@code AtomicLongMap}.
     */
    public Map<K, Long> asMap() {
//      Map<K, Long> result = asMap;
//      return (result == null) ? asMap = createAsMap() : result;
      return createAsMap();
    }

    private Map<K, Long> createAsMap() {
        Map<K,Long> resultMap = new LinkedHashMap<K, Long>();
        if(map != null && !map.isEmpty()){
            for(Entry<K, AtomicLong> entry : map.entrySet()){
                resultMap.put(entry.getKey(), entry.getValue().get());
            }
        }
        return Collections.unmodifiableMap(resultMap);
    }

}